1. Field of the Invention
The present invention relates generally to the monitoring and processing of Internet Protocol (IP) data transferred in an asynchronous transfer mode (ATM). More specifically, the present invention relates to the monitoring of data to determine if it complies with a certain set of rules for further processing, depending on the data flow classification, as the data is transmitted through an ATM switch. The application entitled “A Method and Apparatus for Wire-Speed Application Layer Classification of Data Packets” (U.S. patent application Ser. No. 09/547,034, now abandoned) is assigned to a common assignee. The '034 application is herein incorporated by reference for all purposes.
2. Description of the Related Art
Data flows between a network of computers carrying portions of digital information between different nodes. Generally, the results of an application running at one network node may be sent to a computer at another network node. In order to establish the transfer of data, the information is encapsulated in data packets and transmitted over the network. Some communication protocols transfer data packets in a half duplex mode, while others transfer data packets in a full duplex mode.
Two popular ways of transferring Internet Protocol (IP) data between network nodes are the asynchronous transfer mode (ATM) and the Ethernet packet format mode. FIG. 1 describes a network 100 enabling the transfer of data from one Ethernet network 110 to another Ethernet network 110 through an ATM network 120. The Ethernet networks 110 are connected to the ATM network 120 via ATM gateways 130. However, the method used to transfer packets over the Ethernet networks 110 is different from the method used to transfer data over the ATM networks 120. One difference between the two methods is that the data packets (i.e. “ATM cells”) in the ATM networks 120 have a fixed size, while the data packets (i.e. “Ethernet packets”) in the Ethernet networks 110 vary in size. Another difference is that the ATM cells arrive at their destination in the same order in which they were transmitted from their source, while the Ethernet packets may arrive at their destination out of order.
The ATM is a communication technology designed to address long distance communication at high speeds with different networking systems connected at the end points. Unlike other communications protocols, the ATM transfers cells of data using fixed-length cells, each containing 53 bytes. As shown in FIG. 2, an ATM cell 200 has a 5-byte header 205 and contains a 48-byte payload 210. By using cells 200 having a fixed size, transfer speeds are increased and delay variations are very low. This allows for a dependable performance of the delivery system. The addressing system used for ATM, which was defined by standard committees, depends both on the end system and on the network node to which it is connected. Every network system or node is allocated a 13-byte network address, usually used by the routing protocols, to locate and find a path to a target. The header 205 of the cell 200 contains both a virtual channel identifier (VCI) 215 and a virtual path identifier (VPI) 220 to uniquely identify the channel and path of the cells 200 through the ATM network.
In contrast to the ATM networks 120, Ethernet networks 110 use a scheme based on IP addresses of the data packets to route payloads through a network in accordance with a full duplex protocol. The IP uses a unique identification for a process flow, also known as the IP tuple, which is shown in FIG. 3. Specifically, the IP tuple 300 uniquely identifies a source of a data packet via a 4-byte source IP address 310 and a 2-byte source port 340. Also, the IP tuple 300 uniquely identifies a destination of the data packet by a 4-byte destination IP address 320 and a 2-byte destination port 350. In addition, a 1-byte protocol field 330 defines the protocol type used. Data is transferred over packetized networks, such as an Ethernet, by sending packets of data of variable sizes from a source to a destination, and the packets all have at least the tuple described for identification purposes.
In certain applications the tuple can be extracted from up to 64 bytes. Hence, there are cases where an IP tuple must be split between two ATM cells, as one ATM cell may carry a payload of no more than 48 bytes.
In an Ethernet network, data packets may be monitored for basic qualities in order to apply certain rules regarding such packets. For example, the IP tuple 300 of each data packet may be analyzed to determine the process flow to which it belongs, how the packet should be processed, where the packet should be routed, etc. The application of certain rules to certain data packets ensures a high quality of the transmission of real-time applications such as video or voice over Ethernet, avoids the transmission of restricted applications, and/or applies sets of other rules. However, as higher transmission speeds are required and the number of rules increases, it is essential to design systems that are efficient in handling the stream of packetized data transmitted through the system and that quickly and accurately apply rules to data packets. Since there is a common need to connect between ATM and packetized networks for the purpose of transferring data from one node to another in a mixed network, various ways have been proposed to accomplish this connection. One manner to more efficiently monitor the data in a mixed network is to monitor the IP data when flowing through an ATM node as part of an ATM cell.
While IP data can be classified for purposes of rule checking and enforcing actions by uniquely identifying its characteristics based on information contained in the header, it is essential to extract the header information from the ATM cells. The trivial approach would be to segment and reassemble (SAR) the IP data from the data in each cell. However, although this straightforward approach is simplistic, it requires the reassembly of the entire IP data packet and/or IP tuple, and will degrade the wire-speed performance of the system.